He has very publicly rejected the “prison works” nostrum of Lord Howard, his old Cambridge sparring partner. The two have been political rivals for nearly half a century. In the last Conservative government, Lord Howard followed Mr Clarke at the Home Office and dismantled many of the liberal policies he inherited.

Right-wing Tories reckon Mr Clarke is intent on settling that score with a series of proposals to keep criminals out of custody.

In his first speech in the job last June, he described the size of the prison population as “astonishing”, said short-term sentences were ineffective in most cases and labelled aspects of penal policy as little more than “warehousing criminals”. And then came the cuts.

In October’s Comprehensive Spending Review, the Ministry of Justice faced a budget cut of 23 per cent by 2014, or a £1.6 billion drop to £7.3 billion a year. It will result in the loss of about 14,000 jobs, of which 11,000 are expected to be front line.

Mr Clarke predicts his sentencing reforms will result in a cut in the prison population of 3,000 over the spending period — down from 85,000. In real terms, that will mean tens of thousands fewer criminals going to jail over the next four years and will represent the most sustained reduction in prison numbers since the mid-1950s.